Without any investment in Canon lenses, I would definitely go for the D600. I love my 5D Mark III, but mostly because it is a Canon body and I have a some really nice Canon lenses. The lenses are the heart of a camera system. The bodies come and go. This generation Sony have pushed the absolute image quality of the Nikon bodies ahead. But I love my Canon L primes too much to give them up. If I didn't have those and I was starting out now I would definitely go for the D600. It has about the same resolution (24 mp vs 22.3 mp for the 5D Mark III), but the dynamic range of the Exmor sensor is significantly better (14 stops vs 11 stops) without sacrificing much in the way of shooting speed (5.5 for the D600 vs 6 for the 5DD Mark III). The D600 is kind of like the true successor to the D700, but it's a lot less expensive! It's a great deal of camera for $2000. The main advantage of the 5D Mark III is the autofocus system, which is spectacular. So you need to weigh whether that autofocus system is worth the extra money and loss of DR for you.